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Don't let nondeductible capital losses take you by surprise. Learn the rules for capital losses in 2014.

Sally is a new Fool contributor for 2014, but a long-time personal finance writer, columnist, and certified public accountant. Sally wrote "Help! I Can't Pay My Bills" for St. Martin's Griffin.

When you sell assets that have gone down in value, at least there's one bright spot: You can take a tax deduction on your loss.

Or can you?

Some capital losses may only be partially deductible, or you may not be able to take a deduction until a later year. In fact, some capital losses are not deductible at all.

So before you count on a capital loss for a deduction, check out the rules for these five capital losses in 2014.

Capital losses that exceed capital gains by more than $3,000You generally cannot take a net capital loss for more than $3,000 in any tax year. For example, say you have a $13,000 capital loss from a stock you sell in 2014. You expect to reduce your taxable income by $13,000. Not so fast. You can only use up to $3,000 in capital losses to reduce most taxable income.

If you have capital gains in 2014, you can offset them with capital losses. That's why it's smart to look around for assets you may want to sell at a gain when you sell another asset at a loss, and vice versa. Remember to always make good investment decisions first and tax-planning decisions second.

If you cannot take all your capital-loss deductions in one year, you can carry them forward to the following year.

Capital losses from rental real estate if your income is too highOwning rental real estate has been a favored method for deferring taxes for decades. Thanks largely to the depreciation deduction, you might be able to take tax losses every year, while your property (hopefully) went up in value. The rental-losses allowance is limited to an allowance of $25,000 per year, or $12,500 if you are married filing separately and have lived apart from your spouse all year.

To qualify for this allowance, you must actively participate in the management of your rental property. You also may be subject to "at-risk" rules if not all of your investment is at risk.

Taking a loss on rental real estate is not so easy anymore, especially if you have significant other sources of income. If your modified adjusted gross income, or MAGI, is between $100,000 and $150,000, the maximum amount you can deduct is phased out. If it's over $150,000, you're out of luck. If you're married filing separately, the allowance phases out between $50,000 and $75,000.

You can carry forward any loss not allowed under these rules to the following years.

Losses on personal propertyIs your house worth less than you paid for it? Losing money on your home can be a big financial hit, but the IRS doesn't care. You cannot take a loss on your home, furniture, personal car, or other personal belongings.

The flip side is that when you buy another house that goes up in value, you probably won't have to pay tax on the gain. So that's a plus.

Capital losses for which your investment is not all at riskThe IRS considers something to be "at risk" if you can lose all of your investment in it. If that's the case, you don't have to worry about at-risk rules.

Otherwise, if you're not fully at risk, you cannot deduct a loss for more than the amount you have at risk.

Capital losses on securities you replace within 30 daysYou have a stock that's down, but you still have faith in it. You sell it at a loss, but when it starts to show signs of life, you buy it back.

If you were in too much of a hurry, you may have just lost your tax-deductible loss for the year. If you sell stock or securities and buy substantially identical stock or securities within 30 days before or after the sale, you just made a "wash sale." The loss won't reduce your income this year. It will reduce your basis in the replacement stock when you eventually sell it, however.

Know the rules before you sellMake sure you know the tax ramifications of a sale before you commit to selling an asset. When you understand how a gain or loss affects your total tax situation, you can plan your tax year accordingly, so stay abreast of the rules regarding capital losses in 2014.